The invention relates to two-component cartridges for plastic materials such as sealing materials, cements, dental form materials or other materials. Such cartridges comprise two chambers which are often arranged co-axially and are often formed by two tubular bodies which are disposed one in the other at their front areas. A first chamber is formed by the interior space of the inner tubular body and second chamber is formed as an annular chamber between the outer and the inner tubular body. At their rear ends, the two tubular bodies are held in their concentric positions by an annular piston closing the outer annular chamber between the tubular bodies.
The concentric front end areas of the two tubular bodies inserted into one another have discharge openings for the material components disposed in the inner, first chamber and, respectively, the outer second chamber. Up to its use, the two-chamber cartridge is closed by a closing cover, by which it can also be closed during an interruption of its use. For use a mixer is mounted onto the discharge neck of the outer tubular body, which includes a mixing tube in which a number of mixing structures are arranged axially one after the other so as to mix the first material component discharged from the first chamber with the second material component discharged from the second chamber as fast as possible and as homogenously as possible. At the end of the mixing tube, a completely homogenous mixture of the two material components is then supposed to be discharged.
However, it is well-known that such two-component cartridges have problems which, in spite of substantial efforts, have not yet been solved.
One problem is that it must be made sure that the two material components remain completely separated before use that is they must not come into contact with each other in order to prevent a premature reaction between the two material components and their curing or hardening. To this end, it is necessary that, on one hand, the cover completely closes the discharge arrangement of the two tubular bodies completely and tightly and that, in addition, the cover provides for a sealing separation of the discharge opening of the first chamber and that of the second chamber.
A second problem concerns the design of the mixing system which should provide for a homogeneous mixing of the two material components in a mixing tube which is as short as possible and includes as few as possible mixing elements because the required discharge pressure of the two-component cartridge is of course larger the larger the number of subsequent mixing element in the mixing tube is, since each additional mixing element increases the flow resistance. This problem becomes more important the more viscous, the material components to be pressed out of the chambers are.
In order to make the mixer to be threaded onto the discharge neck of the two-component cartridge as short as possible and provide the smallest possible number of mixing elements, the two material components are divided already in the discharge structure into a plurality of strands which enter the mixer and, in this way, accelerate the mixing procedure.
To this end, WO 2005/0925225 A1 discloses a two-component cartridge consisting of two co-axially arranged tubular bodies which, in the area of the concentric discharge passages of the two tubular bodies are formed in such a way that the first material components discharged from the first chamber as well as the second material component discharged from the second chamber are divided into several strands, wherein all material strands form in the discharge neck an annular arrangement in which the material strands of the first material component and those of the second material component are arranged alternately.
The neck section of the inner tubular body, which is disposed in the neck section of the outer tubular body, is provided with an annular arrangement of separate segment-like or cylindrical discharge channels, which is disposed star-like in the discharge neck of the outer tubular body. The circumferential intermediate chambers disposed between the individual discharge channels of the inner annular body which form the discharge passages for the first material component form the discharge passages for the second material component. The circumferentially alternate material strands of the first material component and the second material component then enter the inlet end of the mixer as a parallel strand bundle.
In this known arrangement, it is however disadvantageous that the material strands of the first material component and of the second material component reach the inlet end of the mixer as parallel strands because they are guided over the full length of the neck arrangement through parallel passages so that, without any transverse flow component present in the material strands, mixing is initiated only by the first mixing element of the mixer.
A further disadvantage of the arrangement described resides in the fact that the cover needs to close each of the outlet passages of the discharge neck of the inner tubular body individually and consequently requires the provision of a plug for engaging into each outlet passage. Complete sealing of such an arrangement however is hard to achieve with a cylindrical plug for a cylindrical discharge channel and much more difficult for an annular array of discharge passages. In each case, the closure cap needs to comprise two parts and include a central plug part on which the closure plugs to be inserted into the discharge passages are formed and also a threaded sleeve which can be threaded onto discharge neck of the outer tubular body.
It is the object of the present invention to provide an arrangement which provides for improved mixing of the material components in a relatively short discharge neck of the two-component cartridge.